Graphical user interface to view man page?

At the command line try examples:

yelp man:printf
yelp 'man:printf(3)'

or use

yelp man:printf & 

to carry on working at the command line. For a more permanent solution try adding

man () { yelp "man:$@"; }

to the last line of your .bashrc file. Then at the command line try examples:

man printf
man printf &

for the yelp viewer to come up. I like having the scroll-able window next to my CLI to alt-tab to.

KDE Helpcenter

KDE Menu > Applications > Help > Unix manual pages

Quick launch

By the khelpcenter help

:~$ khelpcenter --help
Usage: khelpcenter [Qt-options] [KDE-options] [url] 

The KDE Help Center

Generic options:
  --help                    Show help about options
  --help-qt                 Show Qt specific options
  --help-kde                Show KDE specific options
  --help-all                Show all options
  --author                  Show author information
  -v, --version             Show version information
  --license                 Show license information
  --                        End of options

Arguments:
  url                       URL to display

Command: khelpcenter man:apt will show the apt man page via the KDE help center.

With the quick launcher /1/ Mangonel:

The Mangonel is available from the Ubuntu repositories: http://packages.ubuntu.com/search?keywords=mangonel&searchon=names&suite=all&section=all

KDE kio-man

KDE Help center > Kioslaves > man

Using the man ioslave you are able to read the man pages installed on your system. It is easy to use...

As with any other KDE ioslave, it is possible to enter a URL, like man:/socket in any KDE application.

With the Konqueror - "man:apt"

Other browsers - The KDE System Settings > File Assosiations > html.

How good or bad the parsing of the kio-man html output is depending the picked browser.

The browser can be launched from the KRunner /1/.

The Kubuntu Forums has a topic: 'Graphical man page viewer' /2/ in the How To's section.

Links

1. KDE Launchers: http://www.kubuntuforums.net/showthread.php?59851-KDE-Application-Launchers
2. http://www.kubuntuforums.net/showthread.php?62631-Graphical-man-page-viewer

Gman

From the Ubuntu man page, Gman is a "GTK+ based front-end for man, a good replacement for xman."

Gman provides an index of the man pages installed on your local system and offers several options for viewing the man pages. The default option is to have gman open the man pages within an xterm session. This can be modified to suit your taste with four other options.

The other viewing options available are:

• ghostview
• Evince
• LocalBrowse
• NetBrowse

In order to change the application used for viewing, select View from the menu and then select the radio button next to your preferred application, as shown below:

The last two options require having the man2html package installed on your system and will bring up the man pages in your default browser.